Any surface of a non-biological origin initiates a sequence of unwanted reactions when brought into contact with living tissue or blood. The most well known reactions are those generated by the blood-contacting materials that activate the platelets and the plasma coagulation system leading the formation of a thrombus. Foreign surfaces in living tissue activate the complement and the mononuclear cellsystems, thereby creating inflammatory reactions.
Although the present invention is based on the use of polysaccharides selected from heparin, heparan sulphate and chondroitin sulphate for the purpose of providing stable, biocompatible coatings on intraocular eye lenses, the following discussion and disclosure will be mainly directed to heparin or heparan sulphate. However, it is important to note that the invention is not restricted to these two polysaccharides.
Inmobilisation of the blood-anticoagulant, heparin, to artificial, blood-contacting materials has proven to be a successful approach for achieving a thromboresistant surface suitable for short term use (days and weeks). In tis procedure, the structure characteristics of the endothelial lining of the vascular wall are mimiced by end-point attachment of heparin to the surface.
The surface, prepared by end-point attachment of heparin to a polyamine has the following properties: 1) it is nonthrombogenic, 2) it does not activate the complement system, 3) it does not activate the mononuclear cell system, 4) it adheres and stabilizes growth factors and 5) in general it adheres cells to a much lower extent than other surfaces.
Examples on other products where biocompatible coatings are desired are eye lenses, breast implants, vascular grafts, hip joints etc. The surface in question is excellent also for blood contacting materials.
There are several publications that have described the antiproliferative effect of heparin and heparan sulphate on a number of different cells (smooth muscle cells, epithelial cells). In other publications the growth factor stabilizing and activating effect of heparin has been described.
It is now generally agreed that low molecular weight heparin (less than about 2500 D) inhibits cell growth, whereas high molecular weight heparin (higher than about 6000 D) stimulates cell growth.